ECHINODESMA.TA. 163 



* 14. Antedon briareus. (Plate XIV.) 



Centrodorsal flattened ; 15-20 marginal delicate cirri, formed of 

 a few short joints. .. 



Arms more than 70. 



Krst radials obscured ; second in contact, at least three times as 

 long as they are broad ; third widely triangular. Three distichals, 

 the axiUaxy a syzygy ; two palmars. If there is another division 

 there are again two joints ; no syzygy. The first five or six brachials 

 have nearly even edges ; the succeeding ones are markedly wedge- 

 shaped. A syzygy on the third brachial ; succeeding syzygies rare. 

 . Second pinnules longer than first, very delicate, made up of a 

 number of small joints ; the succeeding pinnules stouter and more 

 fleshy. 



This is one of the species in which there is a very considerable 

 difference in the length of the arms ; here some of the arms may be 

 as much as 110 miUim. long, while others are only 75 millim. 

 There is an interradial plating, extending as far as the distichal 

 axiUary. 



The colour (in spirit) is dark brown. 



Port Denison. 



15. Antedon microdiscns. (Plate XV.) 



Centrodorsal rather large and prominent ; the cirri marginal, in 

 two or three rows, from 30-50 in number, with from 50-70 joints, 

 none of which are markedly longer than broad ; as a rule, the distal 

 two thirds have an inconspicuous dorsal spine, and in the larger 

 specimen the penultimate spine is hardly more conspicuous. 



The ■first radials visible ; aU very short and wide, the second not 

 in contact. Three distichals, the axillary a syz3'gy. Three palmars, 

 the axillary normally a syzygy. The arms may divide again, and of 

 the three joints the axillary may or may not be a syzygy. Probably 

 as many as 90 arms in an adult. The earlier brachials have fairly 

 eveu edges, are well rounded above and flattened at their sides ; the 

 next succeeding are faintly wedge-shaped, the distal edge of each 

 projecting alternately on either side into a slight protuberance ; 

 further out, the wedge-form disappears. The arms generally, though 

 slender, are very firm and stiff and are set very close to one another. 



Syzygies 3, 22-25, 40-41; then from 10-12 joints between 

 each. 



The earlier pinnules exceedingly long in the adult, with very 

 stout slightly keeled basal joints ; the second, which is a good deal 

 longe? than the first, has as many as 50 joints and is quite fine at 

 its free end ; the more distal joints are provided with a spine or tuft 

 of spines. 



The stiff straight arms are about 150 millim. long ; the cirri 

 measure nearly 50 millim. ; the disk, with rounded incisions, ha,s a 

 diameter of about 12 millim. 



The disk and the arms, as far as their last division, are largely 



u2 



